Dry kiln



2 Sheets-Sheet l DRY KILN J. E. lMRlE Filed Nov. 11, 1955 Dec. 8, 1936.

Dec. 8, 1936.

J. E. IMRIE DRY KILN Filed Nov. 11, 1935 2 Sheets-Sheet 2 uaoeooooao 0 Patented Dec. 8, 1936 UNITED STATES PATENT OFFIE 1 Claim.

This invention relates to dry kilns. It is a primary object and purpose of the present invention to provide a dry kiln in which green lumber may be properly dried, utilizing heat for such purpose, and selectively utilizing either a forced or a natural circulation of the air through the lumber to dry and, in effect, season the same. Some types and characters of lumber will stand a forced circulation of air through the same with an accomplishment of rapid drying and seasoning. Others require a slower process of drying with natural circulation only, while with others a combination of both methods may be used. In the beginning there may be a forced circulation of warm or heated air and in the latter portion of the drying a natural circulation of the air. My invention, in a very simple, practical and economical manner, attains such kiln drying of lumber and is available to be used in connection with any and all types or characters of lumber without change in structure of the apparatus used, and with merely a change in the methods of operating the apparatus.

A further object of the invention is to provide a dry kiln structure which is economical to operate using a minimum of power for forced air circulation.

An understanding of the invention for accomplishing the ends stated, as well as many others not at this time enumerated, may be had from the following description, taken in connection with the accompanying drawings, in which,

Fig. 1 is a longitudinal vertical section through a dry kiln equipped with my invention.

Fig. 2 is a transverse section therethrough.

Fig. 3 is a plan and horizontal section, the section being through the kiln enclosure or building, and

Fig. 4 is an enlarged transverse vertical section through one of the groups of steam carrying pipes and the air carrying conduit below the same.

Like reference characters refer to like parts in the diiierent figures of the drawings.

In the structure of the dry kiln, an enclosing building in which the lumber is dried is provided, as indicated at I, which has spaced apart tracks 2 leading into the same for carrying trucks with loads of lumber thereon. The trucks are passed into one end of the building through an opening shown at 3 in Fig. 1, which opening is closed by a suitable door after the trucks with the lumber thereon are inside. The building is supplied with the usual chimney or chimneys 5 extending through the roof for the escape of steam and moisture laden air.

The tracks 2 extend lengthwise of the building. The trucks 5, having lumber piled thereon, as shown at 6, are located at succession on the tracks so as to fill or partly fill the building. While but two of the trucks in alinement are shown in Fig. 1, it is to be understood that the building may be of any desired length for a larger number of trucks. The lumber is piled upon the trucks in two separate stacks at opposite sides and lengthwise oi the trucks as shown, with the boards of the two stacks spaced apart as shown at 1, this space being widened toward the bottom, as at la, so that at the lower inner sides of the stacks of lumber the sides of such spaces 1a diverge downwardly outwardly as best shown in Fig. 2. The boards are piled one above the other with suitable spacers between so that there may be a free circulation of air between the spaced boards of the lumber stacks.

A large number of pipes 8 for carrying steam are located lengthwise and under the central portion of the trucks 5 directly below the widened lower ends of the spaces 1a. In the illustration there are two of these nests of pipes B and the same are connected together at their ends by cross pipes 9. Suitable feeder pipes I0 for carrying steam to the pipes 8 and 9 are provided and there is a return or outlet for the steam, or water condensed therefrom, as indicated at H, with suitable control valves for the pipes shown at l2 in Fig. 1 to control the circulation of steam as to amount that may be flowed through the pipes, more or less of the valves being opened as a control of the steam for passage in greater or less amounts is wanted. Above each nest of pipes 8 a centrally located pipe l3 carrying steam is provided, which has a plurality of small openings in its length and at its upper side for the escape of jets of steam I l. This is desirable at times when the humidity of the air within the kiln is not suificiently high. The humidity may be increased by passing steam through the pipes I3 and permitting it to escape as described.

At each side of each nest of pipe coils 8, there is mounted a vertically positioned plate or board l5. These boards extend downwardly alongside the outer pipes and may be extended downwardly to any desired distance for securing the best effect.

Underneath each nest of longitudinal pipes 8 there is mounted a conduit It for carrying air which, at its upper side, is provided with a plurality of nipples I! extending upwardly very closely to the lowermost pipes of the nest of pipes 8. These nipples have vertical passages therethrough for the outward passage of air. The nipples are located longitudinally the entire length of the conduit I6 in relatively closely spaced apart relation.

Air is forced into the conduits I6 and out through the nipples II by a suitable rotary blower the casing of which is shown at I8, and with its outlet connected by suitable branches to the conduits I6. It is to be understood that the conduits I6 decrease in cross sectional area away from the blower so as to get a proper and substantially uniform outward expulsion of air through the nipples at I! the entire length of said conduits.

A return conduit I9 is located longitudinally between the trucks 5 (Fig. 2). Other conduits of smaller size are located along the sides of the building as shown in Fig, 2. The side conduits 20 have right angle sections 2| (Fig. 3) and the intermediate conduit I 9 has branches at its ends, which lead to inlets 22 at opposite sides of the blower casing I8. The conduits I9, 20 have a plurality of openings in the length thereof at their upper sides for air and steam to enter the same and be carried to the blower casing at the inlet sides thereof. It is apparent therefore that there may be a continuous circulation and recirculation of the air in the kiln building through the lumber. Each of the inlet sides 22 to the blower casing is provided with an air inlet valve 23 which, when the same is turned back to open position, provides for the passage of air from outside of the kiln into the blower.

With this construction, when steam is passing through the pipes at 8 and the blower is operating, air is forced upwardly through the pipes and diverges in an upward and outward direction, as indicated in Fig. 4, and is warmed or heated as it passes through said pipes before passing upwardly through the passages Ia, I and between the boards in the stacks of lumber, drawing moisture from the lumber and, the air losing its temperature and becoming heavier, it drops downwardly and is drawn into the return conduits I9 and 20. The humidity of the air, .as previously stated, may be increased by passing steam through the pipes I3. If at any time the air within the kiln is of too great humidity, instead of the air being drawn through the conduits I9 and 20 back to the blower, the valves at 23 may be opened thereby drawing in outside air which, being colder and heavier, will fill the kiln at the lower part thereof and force the highly humid warmer air outwardly through the vent chimney at 4.

It is also apparent that by properly operating the control valves at I2 only a part of the pipes 8 may carry steam if it should be desirable during any part of the operation of drying the lumber to have such condition. It is also evident that the blower, which is driven by an electric motor may, at times be stopped from operation, in which case the circulation of air will be of a natural and not of a forced character. In either case the plates at I5 provide for a natural drawing in of air around their lower edges to pass by the pipes 8, the air rising as it is heated so that it passes between the boards of the stacks of lumber. When air is forced upwardly through the nipples at IT and thence through the pipes 8 an action somewhat similar and analogous to an injector takes place and much more air passes upwardly past .and through the pipes and is heated thereby than that which is delivered from the nipples at IT. Therefore, the air passage through and heated by the pipes I8 is not solely dependent upon the force of the blower but there is a much greater volume of air passing the pipes and heated thereby than is forced by the blower. This results in a great economy in use of electric current. When the blower is not operated, the steam passing through the coils of pipe at 8 heats the air around the coils which naturally rises, drawing in other air at the bottom to be heated and circulate through the lumber stacks. This is a slower circulation than the forced circulation.

It is accordingly apparent that with this invention there may be any desired type of Warm or heated air circulation provided that may be required for any and all types and characters of lumber. Some lumber may be kiln dried only through the slower natural circulation of air provided solely by the heat from the coils coupled with the plates I5 at the sides thereof. In such cases the blower will not be operated during any of the time that the lumber is treated. Still other lumber requires a more rapid drying of the same during some periods of its treatment than at others. Under such circumstances the blower will be operated during a part of the process and be inactive at other times. This is a very valuable feature of the invention for the reason that there is not required several types of kilns to dry the several types of characters of lumber which are met within practice. One very valuable feature of the invention resides in the construction by means of which the forced circulation of air from the blower also draws in other air from the room not blown in by the blower but drawn in by suction at and around the lower edges of the vertical plates I5 to be heated by the coils 8. This permits a considerable economy in electric current consumption inasmuch as a part only of the air has to be forced in by the blower through consumption of power by the electric motor.

While I have shown one form of the kiln construction it is to be understood that many variations in the structure may be resorted to without departing from the invention. The apparatus may be duplicated for greater widths of the kilns insofar as the hot air carrying and the return conduits are concerned and all connected with a single larger blower. Likewise, instead of the trucks having the lumber piled thereon so that the boards parallel the length of the building, the lumber may be piled so that the boards extend transversely of the length. In such case the heating coils 8 are disposed across instead of lengthwise of the kiln building. In each case however, the nest of coils at 8 will be equipped at each side with a plate I5 and have the air carrying conduits I6 below the same with an air entrance space between the upper side of the air conduit I6 and the lower edges of the plates I5. The lower edges of the plates I5 may be extended to a lower plane than shown in Fig. 4 in many instances where it may be desirable in order to get the best air circulation.

The invention is one of great practical merit. It has been thoroughly tested and tried and is in extensive practical use.

The invention is defined in the appended claims and is to be considered comprehensive of all forms of structure coming within their scope.

I claim:

In a dry kiln, an elongated heating coil located horizontally and including a plurality of pipes for carrying a heated fluid, above which coil lumber to be dried is adapted to be positioned, a vertical plate located lengthwise of said coil at each side thereof, each plate having its upper edge extending a distance above the uppermost pipes of said coil, and a horizontally positioned air conduit located beneath and lengthwise of said coil, said conduit having a plurality of air passage openings at its upper side, an air guiding nipple located around each of said openings, and said pipes being spaced short distances from the adjacent lower edges of said plates, combined with means for forcing air through said conduit and through the openings therein, said nipples being directed toward only the medial portion of said pipes for the purpose described.

JAMES E. IMRIE. 

